Conventionally, as a laser processing device for a sheet metal processing, those using a carbon dioxide (CO2) laser oscillator, a YAG laser oscillator, or a fiber laser oscillator as a laser light source are known. The fiber laser oscillator is superior in the optical quality than the YAG laser oscillator, and has an advantage of extremely high oscillation efficiency and the like. For this reason, the fiber laser processing device using the fiber laser oscillator has been utilized for an industrial use, in particular for a sheet metal processing (a cutting or a welding and the like).
Moreover, in recent years, a laser processing machine using a direct diode laser (DDL) module as a laser light source has been developed. The DDL module superposes laser beams of multiple wavelengths generated by a plurality of laser diodes (LD), and transmits them to a processing head by using a transmission fiber. Then, the laser beams ejected from an end face of the transmission fiber are condensed and irradiated onto a material to be processed (a workpiece) by a collimator lens and a condensing lens and the like.
By the way, in the laser processing, a processing method in which a surface roughness of a cut surface becomes uniform has been pursued (Patent Document 1).
However, in Patent Document 1, no quantitative discussion was made so that a guarantee of uniformity was not sufficient.
Also, there was no discussion regarding laser beams from which laser generation source among laser beams from the above noted various generation sources are optimal for guaranteeing a uniformity.